64640 has 32 divisors (see below), whose sum is σ = 156060. Its totient is φ = 25600.

The previous prime is 64633. The next prime is 64661. The reversal of 64640 is 4646.

It can be written as a sum of positive squares in 2 ways, for example, as 61504 + 3136 = 248^2 + 56^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a nialpdrome in base 16.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 590 + ... + 690.

2⁶⁴⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 64640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (78030).

64640 is an abundant number, since it is smaller than the sum of its proper divisors (91420).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

64640 is a wasteful number, since it uses less digits than its factorization.

64640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 120 (or 108 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 64640 is about 254.2439773131. The cubic root of 64640 is about 40.1328913417.

Subtracting from 64640 its sum of digits (20), we obtain a triangular number (64620 = T₃₅₉).

It can be divided in two parts, 646 and 40, that added together give a palindrome (686).

The spelling of 64640 in words is "sixty-four thousand, six hundred forty".